400099 is the Zip Code of International Airport, Mumbai which is placed at Mumbai district, in Maharashtra state. The full form of PIN is postal index number and it is the render of 6 digit numeric value that You can also call Postal Code, Zip Code, and Pin Code, that express each post offices with a unique number that is distributed into three units like, Zip Code of International Airport is 400099 in which the first digit means 4 that express region of Postal Code means Mumbai and the second digit like 0 that display the sub region and the third means 0 is used for short districts like, Mumbai is the district of International Airport and the last three digits means 099 are used for represent the Post Offices.